The use of injection molding apparatus for producing identity cards has become known, especially in connection with the production of so-called chip cards, An apparatus known from European Patent Application No. EP-A10 267 826 is provided with two mold parts movable relative to each other and enclosing a cavity corresponding to the configuration of the card. The known apparatus produces card bodies with a recess in which a so called module, generally comprising a carrier film with an integrated module and contact surfaces, can be inserted. Such modules disposed on a carrier film are known, for example, from European Patent Application No. EP-A2 0 268 830. In the known apparatus the recess is produced by a core or die protruding into the mold space and corresponding to the contour of the recess. To produce the card one injects molten plastic into the mold space at very high pressure via a nozzle or opening in one mold part. The mold parts must thereby be pressed together such that no plastic penetrates between them. Such over-injection not only leads to a mold mark on the molding but also damages the tool in most cases.
The necessary locking pressure is applied by a so called closing unit (not shown in the aforementioned application EP-A1) which is also used to open and close the tool. The closing unit generally comprises a hydraulically operated knee lever connected at one end with one mold part and at the other end with a strut of the injection molding machine. With the tool structure known from the EP-A1, such a closing unit would be loaded to a particularly high degree since almost the total area of the mold space is perpendicular to the opening direction of the mold. The force acting on the-closing unit is calculated from the injection pressure prevailing in the mold space multiplied by the area of the mold space acting perpendicular to the opening direction, which in this case corresponds to the area of the identity card to be produced. At an injection pressure of about 1000 bars, a closing unit must apply a locking pressure of about 500,000 to 600,000 newtons per card to ensure reliable operation. Closing means with high locking pressures involve an accordingly elaborate design of the injection molding machine and necessarily also increase the machine costs, which ultimately affect the price of the product.
In the known apparatus, the injection opening is located opposite the die producing the recess. This assembly results in a gate mark on the surface of the card which is undesirable in many cases. This can be avoided by shifting the injection opening to the side edge of the mold space, as is known. But this causes the problem that the injected plastic material cannot be optimally distributed mainly behind the die, regarded from the injection opening. This results in quality losses such as joint lines or inclusions of air. Since the cards are sometimes exposed to very strong bending stresses in use, such irregularities in the distribution of material make the card break after a relatively short life.